Physics Investigatory Project: Common Base Transistor

TRANSISTOR COMMON-BASE CONFIGURATION

PHYSIC S

INVESTIGATORY PROJECT Name: Joydeep Naskar Class: XII- Science Roll: School: Kendriya Vidyalaya, IIM Joka Session: 2015-16

INDEX S. No.

Title

1

Acknowledgement

2

Certificate

3

Introduction Experiment

4

5.

-Aim -Materials required -Observation -Result

Bibliography

Acknowledgement I would like to thank the CBSE, for providing me the opportunity to carry out this investigatory project. I also take this opportunity to express my sincere gratitude to my Physics teacher, Mr. Arindam Ojha, PGT Physics (Contractual), for guiding me and imparting a sound base of knowledge pertaining to this topic which ensured the successful completion of this project. I would also like to thank him for unending assistance to enable completion of the exercise.

CERTIFICATE This is to hereby certify that the original and genuine investigatory project has been completed sincerely and satisfactorily by Joydeep Naskar of class XII – Sc. KendriyaVidyalaya IIMJoka, Kolkata, regarding his project titled “To study the effect of various solutes on the elevation of boiling point of

water” as per the CBSE practical work requirement for the session 2015-2016.

Teacher’s Signature

Examiner’s Signature

A transistor is a three terminal active device. The terminals are emitter, base, collector. In CB configuration, the base is common to both input (emitter) and output (collector). For normal operation, the E-B junction is forward biased and C-B junction is reverse biased. In CB configuration, IE is +ve, IC is –ve and IB is –ve.

With an increasing the reverse collector voltage, the space-charge width at the output junction increases and the effective base width ‘W’ decreases. This phenomenon is known as “Early effect”. Then, there will be less chance for recombination within the base region. With increase of charge gradient within the base region, the current of minority carriers injected across the emitter junction increases. The current amplification factor of CB configuration is given by, α= ∆IC/ ∆IE

CIRCUIT DIAGRAM

AIM:

1. To observe and draw the input and output characteristics of a transistor connected in common base configuration. 2. To find current gain (α) of the given transistor.

MATERIALS REQUIRED: 1. 2. 3. 4. 5. 6.

A pnp Transistor Regulated power supply (0-30V, 1A) and a 3-V battery Voltmeter (0-30V) Ammeters (0-50mA) 2 high resistance rheostats Connecting wires

PROCEDURE: INPUT CHARACTERISTICS: 1. Connections are made as per the circuit diagram. 2. For plotting the input characteristics, the output voltage VCE is kept constant at 0V and for different values of VEB note down the values of IE.

3. Repeat the above step keeping VCB at 2V, 4V, and 6V. All the readings are tabulated. 4. A graph is drawn between VEB and IE for constant VCB.

OUTPUT CHARACTERISTICS: 1. Connections are made as per the circuit diagram. 2. For plotting the output characteristics, the input IE is kept constant at 10mA and for different values of VCB, note down the values of IC. 3. Repeat the above step for the values of IE at 20mA, 40mA, and 60mA, all the readings are tabulated. 4. A graph is drawn between VCB and Ic for constant IE

OBSERVATIONS: 1. 2. 3. 4. 5. 6. 7.

Least count of voltmeter Vi = 0.1V Range of voltmeter Vi= 0-5 volts Zero error of voltmeter Vi= No error Least count of voltmeter V0 = 0.1V Range of voltmeter V0=0 to 5V Zero error of voltmeter V0= No error Range of milli-ammeter= 0-50mA

8. Zero error of milli-ammeter= No error

Table for input characteristics Sl.

Base-emitter voltage VEB(V)

Emitter current IE (mA) for VCB= 0V

VCB= -2V

VCB= -4V

1

2.5

0

0

0

2

3.0

0

0

0

3

4.2

0

0

0

4

4.6

5

6

9

5

4.8

20

21

26

6

4.9

38

48

Out of range

No .

Table for output characteristics Sl.

Base-collector Collector current IC (mA) for voltage VCB(V) No IE=5mA IE=10mA .

IE=20mA

1

0

4.5

9.0

19.0

2

1

5.0

9.0

19.5

3

2

5.0

9.0

19.5

4

4

5.5

9.5

19.5

5

5

5.5

9.5

19.5

6

6

5.5

9.5

19.5

7

7

5.5

9.5

19.5

8

8

5.5

9.5

19.5

Table for transfer characteristics Sl.

Emitter current IE Collector current IC (mA) for (mA) No VCB= 0V VCB= -2V VCB= -4V . 1

0

0

0

0

2

5

5

5

5

3

6

6

6

6

4

7

7

7

7

5

8

8

8

8

6

10

10

10

10

CALCULATIONS

RESULT 1. The input, output and transfer characteristics are shown in the adjoining graphs. 2. The current gain, α = 3. The voltage gain, Av =

PRECAUTIONS

1. The supply voltages should not exceed the rating of the transistor. 2. Meters should be connected properly according to their polarities.

SOURCES OF ERROR The transistor may be faulty.

BIBILOGRPAHY Various books and websites were referred while making this project:

1) Physics Textbook for class XII, Part-I, NCERT 2) Physics Laboratory Manual for class XII, NCERT 3) Wikipedia.org 4) ConnectUEdu 5) Youtube.com